Circuit breaker



May 17, 1949. J. M. cUMMlNG CIRCUIT BREAKER Filed Nov. 21, 1944 INVENTOR/mas//mw/)y Ww ATTORN WITNESSES:

Patented May 17, 1949 UNITED vSTATES PATENT 'OFFICE 'CIRCUIT BREAKERJames M. Cumming, Turtle Creek, Pa., assigner to Westinghouse ElectricCorporation, East Pittsburgh, Pa., a corporation of PennsylvaniaApplication November 21, 1944, Serial No. 564,447

(Cl. ZOO-450) Claims. 1

This Jinvention 'relates ygenerally to electric circuit linterrupters,and more particularly to `circuit breakers.

lIn relatively large circuit breakers, -Vsuch as those having one ormore sets of contacts suspended in 'an insulating medium within a tankor similar enclosure, 'a common mode of actuating su'ch--contacts'is byvmeans of 'a ylift rod lextending downwardly from 'the `top of theenclosure. Where the'breaker 'contacts are biased open, the lift rod isrequired to withstand the load imposed by vthis bias, and the vcontactpressure load as Well. With modern operating practice requiring highspeed breaker operation, the impact load on closing the breaker isextremely high, thus requiring a relatively heavy lift rod structure towithstand the forces encountered. Oi course, any increase in mass of theoperating mechanism requires a greater operating force in'order torapidly'accelerate the mechanism to the desired high speed operation.

One object of this invention, therefore, is to provide means for closingcircuit breaker contactsat high speed independently 4oi? the breakerli'it rod.

Another lobject of this invention is to provide a novel karrangement ofhydraulic motion transmitting mechainsm for actuating circuit breakercontacts.

Another object 'of this invention is to provide in a circuit breaker ofthe type having its conta'cts Asuspended from the top of an enclosure,novel means of a compression type for transmitting motion from a pointadjacent the top of the enclosure `to the breaker contacts.

Another 'object of this invention is to provide in a circuit breaker oithe type described having 'contacts 'biased to an open circuit position,a lii't 'rod for controlling llatching of the contacts in the closedcircuit position, `and motion transmitting means independent of the liftrod for closing said contacts at a high speed.

A further object of this invention is to reduce the mass of the partsrequired to be moved 'in actuating circuit breaker contacts so that highspeed operation is possible by the use of 'a minimum 'actuating force.

These and other objects of this invention will become more apparent uponconsideration of cthe 'following detailed description of a preferred'embodiment thereof, when taken in consideration with the attacheddrawing, in Which the singie iigure illustrates a circuit breaker withthe breaker yiafrlll:ish'ovi/i'rin substantially central longitixdnaisection, and with the mechanism in the 2 tank being Yshown partially insection and partially in elevation.

The circuit breaker illustrated is adapted yto be suspended in a tank 2from the tank v`cover 6. For this purpose, a 'pair of insulatingbushings 4 are provided with supporting collars intermediate their ends,and the rbushings are adapted to -extend through Vopenings in tank'cover 6 the supporting collars secured to the cover, Efor "'example, asby ybolts I0. The cove-r y(i is ffadapted to be removably secured to thetank -in any de'- sired manner, such, for example, as by bolts '8.Bushings 4 are each provided with a longitudinally extending bore forreceiving a 4comiiuctznr rod 'l2 adapted to support Aa contact 'assemblyH inside casing 2.

Each contact 'assembly le includes 4a supporte ing bracket I6 at theupper 'end thereof, having athre'aded socket for threaded engagementwith the lower end of bushing'conductor rod l2. `Each supporting bracketl5 is of a goodfelectricalcom ducting material, and is adapted to have'si'ipport ing plates 18 Vsecured lto opposite sides thereof, forexample, as by bolts I9. Supporting plates 11 should be off'insulatingmaterial, 'andare 'adapted to support therebetween a plurality oi hollowarc-extinguishing casi-rigs '20 in spaced relation. Thearc-extinguishing casing's 20 may Ib'e "of 4solid construction, butpreferably v'are composed of a plurality of superposed plates ofinsulating inalierial, as shown more particularly in the patent to J. B.MacNeill No. 2,192,772, on a `('il'clli', in'- terrupter, issued March5, 1940, to the same-fassignee as this invention. The`arc-ezuin-gi'iisnin'g casings 20 are adaptedto be secured between'supaporting plates I'S by through bolts -2'I, 4and each casing isprovided with an opening l'at the t'o'p for receiving fa contact projecticn 'Z2 fo'ne'd integral with a contact support 2'4. Each 'cntactsupport 24 is mounted for limited pivotal moyement at one end by a pivotpin l26 extending between supporting plates IS, and 'each Acontar/tsupport is biased for movement of its contact projection 2'2 in adirection to in 'ove 'into its associated arc-extinguishing 'casing 20,by a coll compression spring 28 reacting between the -chtact support'-24 and a stationary 'support fs'uch the arc-extinguishing casingimmediately there above, or in the case olf the uppermost arc-'extinguishing 'casii1g,'its spring '28 reacts 'against supportingbracket i6. Movement of each contact projection `22 into its vassociatedarmemguishin'g 'casing 20 is limited by engagement fof contactsupport 24with 'the upper side xof the nrceX-tinguishing casing. 'The 'Contactsupport M associated with the uppermost arc-extinguishing housing 28 isadapted to be electrically connected with supporting bracket I6 by aflexible shunt 36.

Each arc-extinguishing casing 28 has a movable contact 82 associatedtherewith, which is mounted for pivotal movement about a pivot pin 34extending between supporting plates I8, so as to be movable toward andaway from its associated contact projection 22 through a suitableopening provided in the hollow arc-extinguishing casing 20. Thearc-extinguishing casing 2l) may also be provided with side ventopenings to provide for the relief of uid pressure built up within thecasing when the contacts separate, and to provide for a flow of fluidlaterally through the arc upon separation of the contacts, in the mannershown in the aforesaid MacNeill patent. Each movable contact 32 iselectrically connected with the contact support 24 immediately below itby a flexible shunt 38, and the lowermost movable contact 32 iselectrically connected with a pair of stationary contact jaws 42, bymeans of a flexible shunt 40. The contact jaws 42 of the pair of contactassemblies i4 are adapted to be bridged by a bridging contact bar 44mounted on a movable lift rod 46 of an insulating material, preferably amolded insulating material.

The movable contacts 32 of each contact assembly I4 are connected formovement together by a connecting link 48 pivotally connected with eachmovable Contact by means of pivot pins 58. Connecting link 48 isprovided at its lower end with a latch groove 52 for cooperation with aball latch 54, to releasably latch the movable contacts in engagementwith relatively stationary Contact projections 22, with pressure springs28 stressed a predetermined amount. A movable latch retainer 56 stresseda predetermined amount. A movable latch retainer 56 is adapted to beheld in a position to retain ball latches 54 in engagement with latchgrooves 52 in the closed circuit position of the breaker, by engagementof a head 58 provided on the lower end of retainer 56, with the bridgingContact bar 44. A release spring 6D reacts between head 58 of latchretainer 56 and the lower end of each contact assembly I4, so that whenbridging contact bar 44 is moved downwardly to disengage contact jaws42, latch retainer 56 will be moved downwardly by release spring 6Fl topermit ball latch 54 to escape from latch groove 52, and permit movablecontacts 32 to rapidly disengage contact projections 22, under theinfluence of contact opening spring 62, which reacts between astationary pin 59 anchored in supporting plates I8, and a pin 6Iprovided on connecting link 48.

In order to reclose movable contacts 32 against opening spring 62, thereis provided hydraulic motion transmitting means supported on eachcontact assembly by means of a bracket 64 having a supporting vsleeve66, adapted to be supported above and substantially in alignment withconnecting link 48. Supporting sleeve 66 is adapted to threadedlyreceive the lower end of a cylindrical conduit 68 of insulatingmaterial, such for example as a molded insulating material. Acylindrical pump sleeve I8 is adapted to be threaded on the upper end ofconduit 68, and a bracket 'Il'y connects pump sleeve 'I0 to cover 6, torigidly support the pump sleeve and upper end of conduit 68. A piston'I2 is provided in the lower "end of conduit 68, and this piston has apiston .rod I4 secured to the upper end of connecting 'links 48. Piston'I2 may have its own biasing spring 'I6 which reacts between the pistonand the upper end of its associated contact assembly I4, to bias thepiston 'l2 in a direction to cause opening of contacts 32. A pump piston'i8 is provided in pump cylinder and it has a piston rod 8U connected toa retrieving spring 82 reacting between piston rod 86 and cover 6, for apurpose to be described.

Pump piston 'I8 is adapted to be actuated by an operating rod 34 securedto the upper end of lift rod 46, and having a shoulder 86 adapted toengage one end of an actuating lever 88, which is pivotally mountedintermediate its ends on a bracket 90 supported from cover 6, and lever88 is connected with piston rod 8llat its other end.

The operation of the circuit breaker described above will now beapparent. If it is assumed that the breaker is in its closed-circuitposition illustrated in the drawing, the circuit may be opened by movingoperating rod 84 downwardly. This releases ball latches 54 in the mannerpreviously described to permit opening springs 62 to rapidly separatemovable contacts 32 from contact projection 22. This downward movementof operating rod 84 and lift rod 46 may be very small, for example aboutone-half inch, and as a matter of fact the contacts may be opened sorapidly by opening spring 62 that they will be fully opened beforebridging contact bar 44 is disengaged from contact jaws 42. Pump piston'I8, being larger than piston 12, needs to be retrieved only a shortdistance by its retrieving spring 82, to permit suicient flow of liquidthrough conduit 68 that pi-ston 'l2 is not checked in the circuitopening movement of connecting link 48, but this movement is actuallyassisted by piston spring 76. Opening movement of operating rod E4 willcontinue of course, until bridging contact bar 44 reaches substantiallythe position shown in dotted lines on the drawing, to assure a safe gapin the circuit, and thu-s prevent restriking of the arc after circuitinterruption. The rapid opening movement of movable contacts 32 and theaction of arc-extinguishing casings 26 contribute to obtain rapidextinguishment of the series arcs drawn during circuit opening in theseveral arcextinguishing casings 28. Since tank 2 is adapted to be lledsubstantially to the level L by an arcextiguishing liquid, this liquidwill fill the arcextinguishing casings 28 so that when the contactsseparate therein, and an arc is drawn, gases will be formed to createpressure within each arcextinguislring casing 26 and 'cause a blast ofgas substantially transversely through the arc and out the ventopenings. This flow of fluid through the arc, together with the rapidopening movement of the contacts and confinement of the arc within thearc-extinguishing casings, contributes to rapid and eiiicient arcextinction, as pointed out in the above-mentioned MacNeill patent.

In closing the circuit breaker. operating rod 84 is moved upwardly fromthe dotted line position shown on the drawings, and this results inbridging bar 44 moving into engagement with contact jaws 12, andthereafter shoulder 86 on the operating rod engages actuating levers 88to move pump pistons 'i8 downwardly, thereby exerting pressure on theliquid entrapped between pump piston 'i8 and piston 'i2 in conduit 68,to cause downward movement of piston 'I2 and consequent closing movementof movable contacts 32. This reclosing movement of contacts 32 mustovercome opening spring 62 and stress the same suiiiciently to causerapid opening of the contacts, and, in addition, suicient force must beemployed to stress each contact pressure spring 2B. Also, it is highlydesirable that the closing movement of the breaker beas` rapid ass'possible, which means that relatively large forces are requiredtoaccomplish closing of the breaker contactsbecause of' the high forcerequired to prevent rebounding and consequent momentary separation ofthe contacts, at the moment of initial contact or impact of thecontacts.

Itwill be observed that in the breaker construction described above, theoperating force is transn'ii'ttedy from operating rod 84 which may be ofsteel or similar material having a relatively high strength, and thatthe lift rod 4S- may be relatively light because it is relieved of theforce required to actually close the breaker contacts, and the onlyforce it is required to withstand is that necessary to engage anddisengage bridging barv 44 with contact jaws 42, and to compressrelatively light latch release springs Bil. This is of considerableimportance because lift rod 4S must be of an insulating material, andif' it were required to carryy the contact closing load, it would haveyto be excessively large and massive construction. Accordingly, it is notonly possible; to obtain faster contact movement with the operatingmechanism disclosed herein due to the lighter constructionoi the parts,but faster opening' movement of the contacts is possible dine to thesmall movement of lift rod 45 needed to open the contacts. In otherwords, it is possible withy this `construction to obtain opening of thevcontacts in a shorter time after initiation of movement of the contactoperating mechanism.

Operating rod- 84 may be operated in any desired manner. and there isillustrated for this purpose abell cran-l: 92 pivotally mounted oncasing cover 6 and having a slot Sill in one arm for receiving a pin96'r on the operating rod, with thel other arm of the bell crank pivotedto a connecting rod 98, which in turn is operably connected to a pushrod lllZ mounted alongside elisir-'rgy 2` by a second` bell crank intl.Push rod F02' may be actuated in any desired manner, such for example asby actuating means IM mounted on the breaker casing adjacent the lowerend thereof. Operating means w4- may comprise any well known operatingmeans, such as a solenoid or the like.

Having described preferred embodiments of the invention in accordancewith the Patent Statutes, it is desired that this invention be notlimited to the particular structure disclosed herein inasmuch as it willbe obvious particularly to persons skilled in this art, that manychanges and modifications may be made in this particular structurewithout departing from the broad spirit and scope of this invention, asdeiined irrthe following claims.

I claim as my invention:

l. In a circuit breaker, a liquid container having side, bottom and topwalls, separable contacts 'supported from said top Wall so as to bepositioned in said container below the liquid level thereof, saidcontacts being biased apart to an open circuit. position, means locatedadjacent said contacts for lat'ching said contacts closed, actuatingmechanism supported on said top Wall, liquid motion transmitting meansalso supported from said top wall and connected between said mechanismAand contacts. for closing said contacts against .said bias when saidmechanism is operated in one direction, and said mechanism ,having arelatively ylight movable rod which is separate from said motiontransmitting means and contacts and extends downwardly in said containerinto proximity with said latchingA means for releasing said latchingmeans by movement independent of.` said contacts in response tooperation of said mechanism in thev opposite direction.

2. In a circuit breaker, a container, a, pair of spaced bushings ofinsulating material extending into said container, a conductor in eachof saidl bushings, an. interrupting structure mountedy on each of saidbushings, each of said structures having at least one set of separablecontacts which are biased apart and are adapted to control the circuitthrough said: conductors, a contact on the outer end of eachinterrupting; structure, a movable bridging contact for bridging theouter contacts of said interrupting structures, actuating mechanism forope-rating said contacts, said mechanism including a movable rodcarrying said bridging contact at its outer end, means to releasablylatch said separable conta-cts closed, and mean-s controlled by initialopening movement. of said rod prior to separation of said bridgingcontact from said outer contacts for releasing said latch means andpermitting said separable contacts to separate under thev iniiuence oftheir bias to open the circuit, after which said bridging contact ismoved by said lift rod to insert a relatively large gap in the circuit.

3'. In a circuit breaker, a container, a pair of spaced bushings ofinsulating material extending into said container, a conductor in eachof said bushings, an interrupting structure mounted on each of saidbushings, each of said structuresv having at least one set of separablecontacts which are biased. apart and are adapted to control the circuitthrough said conductors, a contact on the outer end of each interruptingstructine,v a movable bridging contact for bridging the outer contactsof said interrupting structures, actuating mechanism for operating saidcontacts, said mechanism including a movable rod carrying said bridgingcontact at its outer end, meansv to releasably latch said separablecontacts closed, means controlled by initial opening movement of saidrod prior to separation of said bridging contact from said outercontacts for releasing said latch mean-,s and permit said separablecontacts to separate under the influence of their bias to open thecircuit, after which said bridging contact is moved by said rod toinsert a relatively large gap in the circuit, and means cooperative withsaid rod at a point adjacent the other end thereof for reclosing saidseparable contacts in responsey to reverse movement of said rod.

4. In a circuit breaker, a container, a pair of spaced bushings ofinsulating material extending into said container, a conducto-r in eachof lsaid bushings, an interrupting structure mounted on each ofsaidbushing-s, each of said structures having at least one set ofseparable contacts which are biased apart and are adapted to control thecircuit through said conductors, a contact on the outer end oi eachinterrupting structure, a movable bridging contact for bridging theouter contacts oi said interrupting structures, actuating mechanism foroperating said contacts, said mechanism including a movable rodcarrying. said bridging Contact at its, outer` end, means to releasablyvlatch said separable contacts closed, means controlled by initialopening movement of said rod prior to separation of said bridgingcontact from said outer contacts for releasing said latch means andpermitting said separable contacts to separate under the influence oftheir bias to open the circuit, after which said bridging Contact ismoved by said rod to insert a relatively large gap in the circuit, andmeans cooperative with a portion of said mechanism for reclosing saidseparable contacts in response to reverse movement of said rod.

5. In a circuit breaker, a container, a pair of spaced bushings ofinsulating material extending into said container, a conductor in eachof said bushings, an interrupting structure mounted on each of saidbushings, each of said structures having at least one set of separablecontacts which are biased apart and are adapted to control the circuitthrough said conductors, a contact on the outer end of each interruptingstructure, a movable bridging contact for bridging the outer contacts ofsaid interrupting structures, actuating mechanism for operating saidcontacts, said mechanism including a movable rod carrying said bridgingcontact at its outer end, means to releasably latch said separablecontacts closed, means controlled by initial opening movement of saidrod prior to separation of said bridging contact from said outercontacts for releasing said latch means and permitting said separablecontacts to separate under the inuence of their bias to open thecircuit, after which said bridging contact is moved by said rod toinsert a relatively large gap in the circuit, means cooperative withsaid rod at a point adjacent the other end thereof for reclosing saidseparable contacts in response to reverse movement of said rod,including liquid motion transmitting means located adjacent saidbushings.

6. In a circuit breaker, a container, a pair of spaced bushings ofinsulating material extending into said container, a conductor in eachof said bushings, an interrupting structure mounted on each of saidbushings, each of said structures having at least one set of separablecontacts which are biased apart and are adapted to control the circuitthrough said conductors, Va contact on the outer end of eachinterrupting structure, a movable bridging contact for bridging theouter contacts of said interrupting structures, actuating mechanism foroperating said contacts, said mechanism including a movable rod carryingsaid bridging contact at its outer end, means to releasable latch saidseparable contacts closed, means controlled by initial opening movementof said rod prior to separation of said bridging contact from said outercontacts `for releasing said ltch means and permitting said separablecontacts to separate under the influence of their bias to open thecircuit, after which said bridging contact is moved by said rod toinsert a relatively large gap in the circuit, and means for transmittingmotion from a portion of said mechanism located adjacent the other endof said rod to said separable contacts when said mechanism is operatedto move said rod to close the circuit, said motion transmitting meansbeing ineiective to transmit motion when said mechanism is operated toopen the circuit.

7. In a circuit breaker, a container, a pair of spaced bushings ofinsulating material extending into said container, a conductor in eachof said bushings, an interrupting structure mounted on each of saidbushings, each of said structures having a plurality of sets ofseparable contacts which are biased apart and are adapted to control thecircuit through said conductors, said sets of contacts being arranged inlongitudinally spaced relation, a contact on the outer end of eachinterrupting structure, a movable bridging contact for bridging theouter contacts of said interrupting structures, actuating mechanism foroperating said contacts, said mechanism including a movable rod carryingsaid bridging contact at its outer end, means to releasably latch saidseparable contacts closed, and means controlled by initial openingmovement of said rod prior to separation of said bridging contact fromsaid outer contacts for releasing said latch means and permitting saidseparable contacts to separate under the influence of their bias to openthe circuit, after which said bridging contact is moved by said rod toinsert a relatively large gap in the circuit.

8. In a circuit breaker, a container, a bushing of insulating materialextending into said container and having an electrical conductortherein, an interrupting structure mounted on the inner end of saidbushing and including at least one set of separable .contacts which arebiased apart and are adapted to control the circuit through saidconductor, a contact on the outer end of said interrupting structure,actuating mechanism including a movable rod extending down into saidcontainer, a contact carried by said rod at its outer end for movementwith said rod into and out of engagement with said outer end contact,means for releasably latching said separable contacts closed, and meanscontrolled by initial movement of said rod in a direction to open thecircuit to release said latching means prior to separation of said rodcontac-t from said lower end Contact.

9. In a circuit breaker, a container, a bushing of insulating materialextending into `said container and having an electrical conductortherein, an interrupting structure mounted on the inner end of saidbushing and including at least one set ci separable contacts which arebiased apart and are adapted to control the circuit through saidconductor, a contact on the outer end of said interrupting structure,actuating mechanism in.. cluding a movable rod extending down into saidcontainer, a contact carried by said rod at its outer end for movementwith said rod into and out of engagement with said outer end contact,means for releasably latching said separable contacts closed, meanscontrolled by initial movement of said rod in a direction to open thecircuit to release said latching means prior to separation of said rodcontact from said lower end contact, and means .cooperative with saidrod at a point adjacent the other end thereof for reclosing saidseparable contacts in response to reverse movement of said rod.

10. In a circuit breaker, a container, a bushing of insulating materialextending into said container and having an electrical conductortherein, an interrupting structure mounted on the inner end of saidbushing and including at least one set of separable contacts which arebiased apart and are adapted to control the circuit through saidconductor, a contact on the outer end of said interrupting structure,actuating mechanism including a movable rod extending into saidcontainer, a contact carried by said rod at its outer end for movementwith said rod into and out of engagement with said outer end contact,means for releasably latching said separable contacts closed, meanscontrolled by initial movement of said rod in a direction to open thecircuit to release said latching means prior to separation of said rodContact from said lower end contact,

and means for transmitting motion from a portion of said mechanismlocated adjacent the other end of said rod to said separable contactswhen said mechanism in operated to move said rod to close the circuit,said motion transmitting means being ineiective to transmit motion whensaid mechanism is operated to open the circuit.

11. In a circuit breaker, a container, a bushing of insulating materialextending into said container and having an electrical conductortherein, an interrupting structure mounted on the inner end of saidbushing and including a plurality of longitudinally spaced sets ofseparable contacts which are biased apart and are adapted to control thecircuit through said conductor, a -contact on the outer end of saidinterrupting structure, actuating mechanism including a movable rodextending into said container, a contact carried by said rod at itsouter end for movement with said rod into and out of engagement withsaid outer end contact, means for releasably latching said separablecontacts closed, and means controlled by initial movement of said rod ina direction to open the circuit to release said latching means prior toseparation of vsaid rod contact from said lower end contact.

12. In a circuit breaker, a container, a bushing of insulating materialextending into said container and having an electrical conductortherein, an interrupting structure mounted on the inner end of saidbushing and including at least one set of separable contacts which areadapted to control the circuit through said conductor, actuatingmechanism mounted on said container, means for actuating said contactsincluding tubular means of insulating material extending between saidmechanism and said contacts, said tubular means adapted to be filledwith liquid, and displaceable means at each end of said tubular meansassociated with said `contacts and mechanism, respectively, to at leastactuate said contacts to closed circuit position in response toactuating of said mechanism in one direction.

13. In a circuit breaker, a container, a bushing of insulating materialextending into said casing and having an electrical conductor therein,an interrupting structure mounted on the inner end of said bushing andincluding lat least one set of separable contacts which are adapted tocontrol the circuit through said conductor, actuating mechanism mountedon said container, means for `actuating said contacts ,including tubularmeans of insulating material extending between said mechanism and saidcontacts, said tubular means adapted to be lled with liquid,displaceable means at each end of said tubular means associated withsaid contacts and mechanism, respectively, to at least actuate saidcontacts to closed circuit position in response to actuation of saidmechanism in one direction, said contacts being biased apart, releasablelatch means for maintaining said contacts in engagement, meansresponsive to actuation of said mechanism in the opposite direction torelease said latch means, Iand said mechanism being movable in saidopposite direction independently of the displaceable means associatedtherewith.

14. In a circuit breaker, a liquid container having side, bottom and topwalls, separable interrupting contacts positioned in said containerbelow the liquid level thereof, said contacts being biased apart -to anopen circuit position, means located adjacent said contacts latchingsaid contacts closed, actuating mechanism suported on said top Wall,liquid motion transmitting means connected between said mechanism andcontacts for closing said contacts against said bias when said mechanismis operated in one direction, separable disconnect contacts in saidcontainer and connected in series circuit relation with saidinterrupting contacts, said mechanism including a relatively lightmovable rod which is separate from said motion transmitting means andsaid interrupting contacts and carries one of said disconnect contactsadjacent its lower end, and means controlled by initial movement of saidrod by said mechanism in opening the circuit to release said latchingmeans by movement independent of said interrupting contacts to permitseparation of said interrupting contacts under the influence of theirbias to open the circuit, after which said one disconnect contact isseparated from the other of said disconnect contacts.

15. In a circuit breaker, a liquid container having side, bottom and topwalls, separable interrupting contacts positioned in said containerbelow the liquid level thereof, said contacts being .biased apart to anopen circuit position, means located adjacent said contacts latchingsaid contacts closed, actuating mechanism supported on said top wall,liquid motion transmitting means connected between said mechanism andcontacts for closing said contacts against said bias when said mechanismis operated in one direction, separable disconnect contacts in saidcontainer and connected in series circuit relation with saidinterrupting contacts, said mechanism including a relatively lightmovable lift rod which is separate from said motion transmitting meansand said interrupting contacts for carrying one of said disconnectcontacts adjacent its lower end, means controlled by initial movement ofsaid rod by said mechanism in opening the circuit to release saidlatching means by movement independent of said interrupting contacts andpermit separa-tion of said interrupting contacts under the influence oftheir bias to open the circuit, after which said one disconnect contactis separated from the other of said disconnect contacts, and anoperative connection between said motion transmitting means and theupper end of said lift rod for closing said interrupting contacts uponmovement of said rod in the opposite direction.

JAMES M. CUMMING.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,086,752 Thornburg 1 July 1.3,1937 2,192,772 MacNeill Mar. 5, 1940 2,249,006 Kesselring et al. July15, 1941

